medRxiv preprint
WHAT IS ALREADY KNOWN ON THIS TOPICThere are several reports about the serum antibodies against SARS-CoV-2. However, most of them evaluate diagnostic accuracy. Only two articles report dynamics of SARS-CoV-2 viral RNA and antibodies with serial samples, but the observation periods are within 30 days. None of the studies investigate the profiles of SARS-CoV-2 viral load and antibodies in a long period. Three reports investigate profiles in respiratory samples, but there are no reports on the dynamics of the viral load in stool samples.
WHAT THIS STUDY ADDSIn both sputum and stool, SARS-CoV-2 RNA persists for a long time. The anti-RBD antibodies may involve in the clearance of SARS-CoV-2 infection. After eight weeks from symptom onset, IgM were negative in many of the previously positive patients, and IgG levels remained less than 50% of the peak levels in more than 20% of the patients. In about 40% of the patients, anti-RBD IgG levels increased 4-time higher in convalescence than in acute phase. Long persistence of SARS-CoV-2 viral RNA in sputum and stool presents challenges for management of the infection. The IgM/IgG comb test is better than single IgM test as a supplement diagnostic tool. Anti-RBD may be a protective antibody, and is valuable for development of vaccines.
ABSTRACT OBJECTIVETo investigate the dynamics of viral RNA, IgM, and IgG and their relationships in patients with SARS-CoV-2 pneumonia over an 8-week period.
DESIGNRetrospective, observational case series.
SETTING
Wenzhou Sixth People's HospitalPARTICIPANTS Thirty-three patients with laboratory confirmed SARS-CoV-2 pneumonia admitted to hospital. Data were collected from MAIN OUTCOME MEASURES Throat swabs, sputum, stool, and blood samples were collected, and viral load was measured by reverse transcription PCR (RT-PCR). Specific IgM and IgG against spike protein (S), spike protein receptor binding domain (RBD), and nucleocapsid (N) were analyzed.
RESULTSAt the early stages of symptom onset, SARS-CoV-2 viral load is higher in throat swabs and sputum, but lower in stool. The median (IQR) time of undetectable viral RNA in throat swab, sputum, and stool was 18.5 (13.25-22) days, 22 (18.5-27.5) days, and 17 (11.5-32) days, respectively. In sputum, 17 patients (51.5%) had undetectable viral RNA within 22 days (short persistence), and 16 (48.5%) had persistent viral RNA more than 22 days (long persistence). Three patients (9.1%) had a detectable relapse of viral RNA in sputum within two weeks of their discharge from the hospital. One patient had persistent viral RNA for 59 days or longer. The median (IQR) seroconversion time of anti-S IgM, anti-RBD IgM, and anti-N IgM was 10.5 (7.75-15.5) days, 14 (9-24) days, and 10 (7-14) days, respectively. The median (IQR) seroconversion time of anti-S IgG, anti-RBD IgG, and anti-N IgG was 10 (7.25-16.5) days, 13 (9-17) days, and 10 (7-14) days, respectively. By week 8 after symptom onset, IgM were negative in many of the previously positive patients, and IgG levels remained less than 50% of the p...
